1. Field of the Invention
The present invention relates to polyisocyanurate foams prepared from partially etherified methylolamines with polyisocyanates in the presence of trimerization catalysts.
2. Description of the Prior Art
The prior art generally teaches the preparation of isocyanurate-modified foam products.
U.S. Pat. No. 4,139,501 teaches the preparation of polyurethane foam with enhanced flame retardancy by the reaction of a polyol and an organic polyisocyanate in mixture with a hydroxylmethylmelamine derivative and including therein a halogenated phosphorus ester.
U.S. Pat. No. 4,197,373 teaches the preparation of flame retardant polyurethane foams from a reaction mixture containing the reaction products of melamine and chloral and optionally alkylene oxide adducts thereof.
U.S. Pat. No. 3,135,707 teaches the use of partially alkylated polymethylolmelamines for the preparation of polyurethane foams. There is no teaching in the prior art that improved flame retardant polyisocyanurate foams may be prepared employing partially etherified methylolmelamines either alone or in combination with other polyols.